fix(mcp): fix CI pre-commit failures for RBAC tool visibility

- auth.py: collapse check_tool_permission signature to one line (ruff-format)
- auth.py: extract _log_user_resolution_failure() helper to reduce
  _setup_user_context cyclomatic complexity from 11 to 10 (ruff C901)
- test_middleware.py: shorten docstring to stay within 88-char limit (ruff E501)